Multi-stage centrifugal pump transition runner and runner design method

Abstract

The invention relates to a multi-stage centrifugal pump transition flow channel and a flow channel design method. The transition flow channel comprises a delivery chamber, a flow channel diffusion section and a suction chamber. An outlet of the delivery chamber located at the upper stage is communicated with an inlet of the flow channel diffusion section, and an outlet of the flow channel diffusion section is communicated with an inlet of the suction chamber; the delivery chamber is of a double-volute structure and is symmetrically arranged about the center line of the volute, and the sum of the areas of the two symmetrical throats is equal to the area of a single volute; the flow channel diffusion section obliquely penetrates through the pump body, the internal sectional area of the flow channel diffusion section is gradually increased in the direction from an inlet to an outlet until the sectional area is equal to or slightly smaller than the inlet area of the suction chamber, the flow channel diffusion section is symmetrically arranged about the center line of the volute, and the suction chamber is symmetrically arranged about the center line of the volute. The radial force can be basically balanced, so that the pump operates stably, and the noise and vibration of a unit are reduced; the radial size of the pump body is small and space is saved; the efficient range is wide; the axial distance of the transition flow channel is reduced, and the axial size of the pump body is reduced.

Description

Technical Field

[0001] The invention relates to a transition flow channel, in particular to a transition flow channel and a flow channel design method for a multi-stage centrifugal pump which can basically balance radial forces, ensure stable pump operation and have a wide range of high efficiency. Background Art

[0002] The flow channel from the throat of the previous volute to the inlet of the next impeller is called the transition flow channel, which is mainly used in multi-stage volute centrifugal pumps. Its main functions are: to lead the outlet of the previous discharge chamber to the inlet of the next impeller; to convert the velocity energy of the volute into pressure energy with minimal hydraulic loss; and to provide a uniform velocity field for the inlet of the next impeller.

[0003] The transition flow channel design method currently used in China adopts a single volute design method for the volute, and the design method of the intermediate transition section is too general and the radial dimension is too large, such as the transition flow channel design method described in the book "Modern Pump Theory and Design".

[0004] The Chinese patent application with announcement number CN 107035720 A applies for a transition channel structure of a multi-stage centrifugal pump and its design method. This structure and its design method have the following problems: 1. The water suction chamber is fully spiral, and there is no specific water suction chamber design method; 2. The cross-sectional area of ​​the upper pressure water chamber of the design method is approximately equal to the arbitrary cross-sectional area of ​​the diffuser elbow, and the overall speed of the liquid from the extrusion chamber to the next suction chamber is basically unchanged, which does not meet the requirements of high-efficiency design. In order to make the flow in the circumferential direction of the impeller more uniform, the liquid should be accelerated into the impeller inlet, and the cross-sectional area of ​​the suction chamber should be designed to be larger; 3. The cross-section of the diffuser section is a trapezoidal structure. Under the same area, when the radial dimensions are equal, the axial distance of the trapezoidal structure is greater than that of the rectangle. The overall structure of the pump becomes longer. Summary of the invention

[0005] In view of the above problems, the main purpose of the present invention is to provide a design method for transition flow channels and flow channels of a multi-stage centrifugal pump which can basically balance the radial force, ensure stable pump operation and have a wide range of high efficiency.

[0006] The present invention solves the above technical problems through the following scheme: a transition flow channel of a multi-stage centrifugal pump, the transition flow channel of the multi-stage centrifugal pump comprises: an extrusion chamber, a flow channel diffusion section and a suction chamber.

[0007] The outlet of the extrusion chamber located at the upper stage is communicated with the inlet of the flow channel diffuser section, and the outlet of the flow channel diffuser section is communicated with the inlet of the suction chamber.

[0008] The extrusion chamber is a double volute structure and is arranged symmetrically about the center line of the volute, and the sum of the areas of the two symmetrical throats is equal to the area of ​​the single volute; the flow channel diffuser section obliquely passes through the pump body, and the internal cross-sectional area of ​​the flow channel diffuser section from the inlet to the outlet direction gradually increases until the cross-sectional area is equal to or slightly smaller than the inlet area of ​​the suction chamber, the flow channel diffuser section is arranged symmetrically about the center line of the volute, and the suction chamber is arranged symmetrically about the center line of the volute.

[0009] In a specific implementation example of the present invention, two flow baffles are cast between the two suction chambers. The baffles are arranged horizontally and have a thickness consistent with the volute wall thickness.

[0010] In a specific implementation example of the present invention, each cross section of the extrusion chamber is a rectangular structure.

[0011] In a specific implementation example of the present invention, each cross section of the flow channel diffusion section is a rectangular structure.

[0012] In a specific implementation example of the present invention, the suction chamber is designed as a semi-circular ring structure, each cross section is a rectangle, and the width of the rectangle is equal to the width b3 of the inlet of the extrusion chamber.

[0013] In a specific implementation example of the present invention, the flow channel diffusion section is designed as a diffusion tube with a diffusion angle, the center connecting line of the diffusion section section is a spatial curve distributed on the cylindrical surface, each section is a rectangle, and the rectangle width is equal to the extrusion chamber inlet width b3.

[0014] In a specific implementation example of the present invention, the arc angle of the flow channel diffusion section is 180 degrees, and the outlet of the previous stage extrusion chamber is introduced into the inlet of the next stage suction chamber.

[0015] A design method for a transition flow channel of a multi-stage centrifugal pump includes: an extrusion chamber is designed according to a velocity coefficient method, each section of the extrusion chamber is designed to be a rectangle, the eighth section area S8 of the extrusion chamber is calculated, S8 is half of the eighth section area of ​​a single volute, and the extrusion chamber inlet width b3 is calculated; the suction chamber is designed to be an annular suction chamber, each section of the suction chamber is a rectangle, and the rectangle width is equal to the extrusion chamber inlet width b3.

[0016] In a specific implementation example of the present invention, the design method includes the following steps: the flow channel diffusion section of the transition flow channel of the centrifugal pump is designed as a diffusion tube with a diffusion angle, the center connecting line of the cross section of the diffusion section is a spatial curve distributed on the cylindrical surface, each cross section is a rectangle, and the width of the rectangle is equal to the extrusion chamber inlet width b3.

[0017] The arc angle of the flow channel diffusion section is 180°, which introduces the outlet of the previous stage extrusion chamber into the inlet of the next stage suction chamber, and the liquid flow direction is turned 180°.

[0018] Based on the impeller inlet area 2S yAs is known, in order to make the flow in the circumferential direction of the impeller more uniform, the liquid should be accelerated into the impeller inlet, so the area S of the cross section AA a / S y =C, C takes a value of 1.5 to 2.2, and a smaller ratio is suitable for the specific speed n s =30~220, the larger ratio is suitable for n s ≧220;

[0019] The area of ​​the cross section CC of the annular suction chamber is equal to the area of ​​the cross section AA, S C =S a =C*S y =D3*b3-d*b3;

[0020] D3—diameter of annular suction chamber;

[0021] d—suction chamber shaft diameter, known;

[0022] Diameter D3 of the annular suction chamber: D3 = C*S y / b3+d(formula 1);

[0023] The inlet area of ​​the flow channel diffuser is approximately considered to be the eighth cross-sectional area of ​​the extrusion chamber, and the outlet area of ​​the flow channel diffuser is the area of ​​cross-sectional area AA. Since the cross-sectional area of ​​the flow channel diffuser is not circular, the area of ​​each cross-sectional area is converted into an equivalent circular area, and the equivalent diffusion angle is calculated:

[0024]

[0025] L is the length of the center connecting line of the diffuser flow channel;

[0026] The center connecting line of the diffuser flow channel is a space curve distributed on the cylindrical surface. When unfolded on the plane, its shape is the diagonal line of a rectangle, so the length of L can be calculated by the following formula:

[0027]

[0028] r—is the projection of L on the plane perpendicular to the axis direction, which is approximately considered to be an arc, and r is the radius of the arc;

[0029] m—is the axial distance between the centers of the discharge chamber and the suction chamber, and is also the axial distance between the starting point and the end point of the center connection line of the diffuser flow channel; m is known;

[0030] By converting formula 2 and formula 3, we can get:

[0031]

[0032] In the formula, the value range of the equivalent diffusion angle θ is 7°~13°;

[0033] Select the θ value and calculate the r value; determine whether the r value is reasonable based on the overall structure of the multi-stage pump. If the r value meets the design requirements, the θ value is feasible; if the r value does not meet the structural design requirements, re-assign θ and calculate the r value until the r value meets the design requirements;

[0034] According to the calculated r value, and knowing the starting point k and end point P of the arc where the radius r is located, the arc can be drawn; point K is the centroid of the eighth section of the volute, and point P is the centroid of the A-A section;

[0035] The flow channel diffusion section is divided into n sections according to the length of L, and the value of n ranges from 2 to 8. The longer L is, the larger the value is. The equivalent circular area of ​​each section is calculated by S8 and the equivalent diffusion angle θ.

[0036]

[0037] Since each cross section of the diffusion section is a rectangle, the width of the rectangle is equal to the width b3 of the extrusion chamber inlet, and the length of the rectangle is the height of the cross section.

[0038] By connecting each section step by step in the order from the inlet to the outlet of the diffuser, the shape of the diffuser flow channel is obtained; the design of the transition flow channel is completed.

[0039] The positive and progressive effects of the present invention are as follows: compared with common similar technologies, the design method of the transition flow channel and flow channel of the multi-stage centrifugal pump provided by the present invention can basically balance the radial force, make the pump run smoothly, reduce the noise and vibration of the unit; the radial dimension of the pump body is small, saving space; the high efficiency range is wide; the axial distance of the transition flow channel is reduced, and the axial dimension of the pump body is reduced. At the same time, the present invention clarifies the design of the suction chamber, the liquid enters the impeller inlet at an accelerated speed, and the flow in the circumferential direction of the impeller is more uniform, which improves the flow of the liquid and improves the efficiency. The present invention uses the cross-sectional area of ​​the extrusion chamber and the suction chamber as a reference, and adopts a gradual diffusion design concept for the diffusion degree of the intermediate flow channel, which is more in line with the flow law of the pump. The overall calculation process is simple, the calculation speed is fast, and the design time is shortened. The present invention is particularly suitable for working conditions with small flow and high head. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is one of the overall structural schematic diagrams of the present invention (line diagram).

[0041] Figure 2 This is the second schematic diagram of the overall structure of the present invention (line diagram).

[0042] Figure 3 This is the third schematic diagram of the overall structure of the present invention (effect diagram).

[0043] Figure 4This is the fourth schematic diagram of the overall structure of the present invention (effect diagram).

[0044] The following are the names corresponding to the labels in the present invention:

[0045] Extrusion chamber 1, flow channel diffusion section 2, suction chamber 3, flow isolation baffle 4. DETAILED DESCRIPTION

[0046] Preferred embodiments of the present invention are given below in conjunction with the accompanying drawings to illustrate the technical solutions of the present invention in detail.

[0047] Figure 1 It is one of the overall structural schematic diagrams of the present invention (line diagram), Figure 2 This is the second schematic diagram of the overall structure of the present invention (line diagram), Figure 3 This is the third schematic diagram of the overall structure of the present invention (effect diagram), Figure 4 The fourth schematic diagram of the overall structure of the present invention (effect diagram) is shown in FIG. Figure 1-4 The transition channel of the multistage centrifugal pump proposed by the present invention comprises an extrusion chamber 1, a channel diffusion section 2, and a suction chamber 3. The transition channel is designed as two symmetrically arranged separate channels, and the sum of the two symmetrical throat areas is equal to the single volute area.

[0048] The outlet of the upper extrusion chamber is connected to the inlet of the flow channel diffusion section, and the outlet of the flow channel diffusion section is connected to the inlet of the suction chamber. The extrusion chamber is a double volute structure, and is arranged symmetrically with the center line of the volute. The sections of the extrusion chamber are rectangular structures, and the sum of the two symmetrical throat areas is equal to the area of ​​the single volute; the flow channel diffusion section passes through the pump body obliquely, and the internal cross-sectional area of ​​the flow channel diffusion section from the inlet to the outlet direction gradually increases until the cross-sectional area is equal to or slightly smaller than the inlet area of ​​the suction chamber. The flow channel diffusion section is arranged symmetrically with the center line of the volute, and the sections of the flow channel diffusion section are rectangular structures; the suction chamber is designed as a semi-circular ring structure, each section is rectangular, and is arranged symmetrically with the center line of the volute. Two flow baffles 4 are cast between the two suction chambers. The flow baffles 4 are arranged horizontally, and the thickness is consistent with the wall thickness of the volute. The flow baffles 4 can reduce eddy currents and turbulence, which is conducive to improving flow distribution, improving efficiency and improving cavitation performance.

[0049] The extrusion chamber is designed according to the velocity coefficient method. In order to facilitate casting and save axial space, each section of the extrusion chamber is designed to be rectangular. According to the velocity coefficient method of "Modern Pump Theory and Design", the eighth section area S8 of the extrusion chamber (half of the eighth section area of ​​the single volute) can be calculated, and the extrusion chamber inlet width b3 can be calculated. In order to facilitate casting, the suction chamber is designed as an annular suction chamber, and each section of the suction chamber is rectangular, and the rectangle width is equal to the extrusion chamber inlet width b3.

[0050] The flow channel diffusion section is designed as a diffusion tube with a diffusion angle. The center connecting line of the diffusion section section is a space curve distributed on the cylindrical surface. Each section is a rectangle, and the width of the rectangle is equal to the extrusion chamber inlet width b3.

[0051] The arc angle of the flow channel diffusion section is 180°, which introduces the outlet of the previous extrusion chamber into the inlet of the next suction chamber, and the liquid flow direction turns 180°. The size of the arc angle is determined according to design requirements. In this invention, Figure 1 , Figure 2 The arc angle shown is 180°.

[0052] According to the known area 2Sy at the impeller inlet, in order to make the flow in the circumferential direction of the impeller more uniform, the liquid should be accelerated into the impeller inlet. Therefore, the area of ​​the cross-section AA Sa / Sy=C, and C takes a value of 1.5~2.2. The smaller ratio is suitable for the specific speed ns=30~220, and the larger ratio is suitable for ns≧220.

[0053] The area of ​​the cross section CC of the annular suction chamber is equal to the area of ​​the cross section AA, SC = Sa = C*Sy = D3*b3-d*b3;

[0054] D3—diameter of annular suction chamber;

[0055] d—suction chamber shaft diameter, known;

[0056] The diameter D3 of the annular suction chamber: D3 = C*Sy / b3+d (Formula 1);

[0057] The inlet area of ​​the flow channel diffuser section can be approximately considered as the eighth section area of ​​the extrusion chamber, and the outlet area of ​​the flow channel diffuser section is the area of ​​section AA. Since the cross section of the flow channel diffuser section is not circular, the area of ​​each section is converted into an equivalent circular area, and the equivalent diffusion angle is calculated:

[0058]

[0059] L is the length of the center connecting line of the diffuser flow channel;

[0060] The center connecting line of the diffuser flow channel is a space curve distributed on the cylindrical surface. When unfolded on the plane, its shape is the diagonal line of a rectangle, so the length of L can be calculated by the following formula:

[0061]

[0062] r—such as Figure 1 As shown, it is the projection of L on the plane perpendicular to the axis direction. It is approximately considered that its projection is an arc, and r is the radius of the arc;

[0063] m—such as Figure 2As shown, it is the axial distance between the centers of the discharge chamber and the suction chamber, and also the axial distance between the starting point and the end point of the center connecting line of the diffuser flow channel. It is known;

[0064] By converting formula 2 and formula 3, we can get:

[0065]

[0066] In the formula, the value range of the equivalent diffusion angle θ is 7°~13°;

[0067] Select the θ value and calculate the r value. Determine whether the r value is reasonable based on the overall structure of the multistage pump. If the r value meets the design requirements, the θ value is feasible; if the r value does not meet the structural design requirements, reassign θ and calculate the r value until the r value meets the design requirements.

[0068] According to the calculated r value, and knowing the starting point k and end point P of the arc where the radius r is located, the arc can be drawn. Point K is the centroid of the eighth section of the volute, and point P is the centroid of the A-A section.

[0069] The flow channel diffusion section is divided into n sections according to the length of L. The value of n ranges from 2 to 8. The longer L is, the larger the value is. The equivalent circular area of ​​each section is calculated by S8 and the equivalent diffusion angle θ.

[0070]

[0071] Since each cross section of the diffusion section is a rectangle, the width of the rectangle is equal to the width b3 of the extrusion chamber inlet, and the length of the rectangle is the height of the cross section.

[0072] By connecting each section step by step in the order from the inlet to the outlet of the diffuser, the shape of the diffuser flow channel is obtained; the design of the transition flow channel is completed.

[0073] The present invention can basically balance the radial force, make the pump run smoothly, reduce the noise and vibration of the unit; the radial dimension of the pump body is small, saving space; the high efficiency range is wide; the axial distance of the transition flow channel is reduced, and the axial dimension of the pump body is reduced. At the same time, the present invention clarifies the design of the suction chamber, the liquid enters the impeller inlet at an accelerated speed, and the flow in the circumferential direction of the impeller is more uniform, which improves the flow of the liquid and increases the efficiency. The present invention uses the cross-sectional area of ​​the extrusion chamber and the suction chamber as a reference, and adopts a gradual diffusion design concept for the diffusion degree of the intermediate flow channel, which is more in line with the flow law of the pump. The overall calculation process is simple, the calculation speed is fast, and the design time is shortened; the present invention is particularly suitable for working conditions with small flow and high head.

[0074] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected, and the scope of the present invention to be protected is defined by the attached claims and their equivalents.

Claims

1. A transition channel of a multistage centrifugal pump, characterized in that: The transition flow channel of the multi-stage centrifugal pump comprises: an extrusion chamber, a flow channel diffusion section and a suction chamber; The outlet of the extrusion chamber located at the upper stage is communicated with the inlet of the flow channel diffuser section, and the outlet of the flow channel diffuser section is communicated with the inlet of the suction chamber; The extrusion chamber is a double volute structure and is arranged symmetrically about the center line of the volute, and the sum of the areas of the two symmetrical throats is equal to the area of ​​the single volute; the flow channel diffuser section obliquely passes through the pump body, and the internal cross-sectional area of ​​the flow channel diffuser section from the inlet to the outlet direction gradually increases until the cross-sectional area is equal to or slightly smaller than the inlet area of ​​the suction chamber, the flow channel diffuser section is arranged symmetrically about the center line of the volute, and the suction chamber is arranged symmetrically about the center line of the volute.

2. The transition channel of the multi-stage centrifugal pump according to claim 1, characterized in that: Two flow isolation baffles are cast between the two suction chambers. The baffles are arranged horizontally and have a thickness consistent with the volute wall thickness.

3. The transition channel of the multi-stage centrifugal pump according to claim 1, characterized in that: Each cross section of the extrusion chamber is a rectangular structure.

4. The transition channel of the multi-stage centrifugal pump according to claim 1, characterized in that: Each cross section of the flow channel diffusion section is a rectangular structure.

5. The transition channel of the multi-stage centrifugal pump according to claim 1, characterized in that: The suction chamber is designed as a semicircular ring structure, each cross section is a rectangle, and the width of the rectangle is equal to the width b3 of the extrusion chamber inlet.

6. The transition channel of the multi-stage centrifugal pump according to claim 1, characterized in that: The flow channel diffusion section is designed as a diffusion tube with a diffusion angle. The center connecting line of the diffusion section section is a space curve distributed on the cylindrical surface. Each section is a rectangle, and the width of the rectangle is equal to the extrusion chamber inlet width b3.

7. The transition channel of the multi-stage centrifugal pump according to claim 1, characterized in that: The arc angle of the flow channel diffusion section is 180°, which introduces the outlet of the previous stage extrusion chamber into the inlet of the next stage suction chamber.

8. A method for designing a transition channel of a multi-stage centrifugal pump according to claim 1-7, characterized in that: The design method includes: the extrusion chamber is designed according to the velocity coefficient method, each section of the extrusion chamber is designed to be a rectangle, the eighth section area S8 of the extrusion chamber is calculated, S8 is half of the eighth section area of ​​the single volute, and the extrusion chamber inlet width b3 is calculated; the suction chamber is designed to be an annular suction chamber, each section of the suction chamber is a rectangle, and the rectangle width is equal to the extrusion chamber inlet width b3.

9. The method for designing a transitional flow channel of a multi-stage centrifugal pump according to claim 8, characterized in that: The design method comprises the following steps: the flow channel diffusion section of the transition flow channel of the centrifugal pump is designed as a diffusion tube with a diffusion angle, the central connecting line of the cross section of the diffusion section is a space curve distributed on the cylindrical surface, each cross section is a rectangle, and the width of the rectangle is equal to the width b3 of the inlet of the extrusion chamber; The arc angle of the flow channel diffusion section is 180°, which introduces the outlet of the previous stage extrusion chamber into the inlet of the next stage suction chamber, and the liquid flow direction is turned 180°; Based on the impeller inlet area 2S y As is known, in order to make the flow in the circumferential direction of the impeller more uniform, the liquid should be accelerated into the impeller inlet, so the area S of the cross section AA a / S y =C, C takes a value of 1.5 to 2.2, and a smaller ratio is suitable for the specific speed n s =30~220, the larger ratio is suitable for n s ≧220; The area of ​​the cross section CC of the annular suction chamber is equal to the area of ​​the cross section AA, S C =S a =C*S y =D3*b3-d*b3; D3—diameter of annular suction chamber; d—suction chamber shaft diameter, known; Diameter D3 of the annular suction chamber: D3 = C*S y / b3+d(formula 1); The inlet area of ​​the flow channel diffuser is approximately considered to be the eighth cross-sectional area of ​​the extrusion chamber, and the outlet area of ​​the flow channel diffuser is the area of ​​cross-sectional area AA. Since the cross-sectional area of ​​the flow channel diffuser is not circular, the area of ​​each cross-sectional area is converted into an equivalent circular area, and the equivalent diffusion angle is calculated: L is the length of the center connecting line of the diffuser flow channel; The center connecting line of the diffuser flow channel is a space curve distributed on the cylindrical surface. When unfolded on the plane, its shape is the diagonal line of a rectangle, so the length of L can be calculated by the following formula: r—is the projection of L on the plane perpendicular to the axis direction, which is approximately considered to be an arc, and r is the radius of the arc; m—is the axial distance between the centers of the discharge chamber and the suction chamber, and is also the axial distance between the starting point and the end point of the center connection line of the diffuser flow channel; m is known; By converting formula 2 and formula 3, we can get: In the formula, the value range of the equivalent diffusion angle θ is 7°~13°; Select the θ value and calculate the r value; determine whether the r value is reasonable based on the overall structure of the multi-stage pump. If the r value meets the design requirements, the θ value is feasible; If the r value does not meet the structural design requirements, reassign θ and calculate the r value until the r value meets the design requirements. According to the calculated r value, and knowing the starting point k and end point P of the arc where the radius r is located, the arc can be drawn; point K is the centroid of the eighth section of the volute, and point P is the centroid of the A-A section; The flow channel diffusion section is divided into n sections according to the length of L, and the value of n ranges from 2 to 8. The longer L is, the larger the value is. The equivalent circular area of ​​each section is calculated by S8 and the equivalent diffusion angle θ. Since each cross section of the diffusion section is a rectangle, the width of the rectangle is equal to the width b3 of the extrusion chamber inlet, and the length of the rectangle is the height of the cross section. By connecting each section step by step in the order from the inlet to the outlet of the diffuser, the shape of the diffuser flow channel is obtained; the design of the transition flow channel is completed.

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